With the progress of high integration and high functionality of a semiconductor device using a silicon single crystal wafer, the silicon single crystal wafer used in device fabrication is becoming larger in diameter. At present, a 200 mm (8-inch) wafer is a main current of the kinds of wafer, but it is expected that a 300 mm wafer will advance into quantity production and in the near future the 300 mm wafer will be a main current thereof. In addition, a 400 mm wafer is thought to follow the 300 mm wafer as the next generation, for which the development is on the way. As a method growing a silicon single crystal ingot for manufacturing a silicon single crystal wafer having a diameter of 300 mm or more, nothing is available other than a Czochralski method (CZ method) in the current state of the art.
Then, it has been known that crystal defects named grown-in defects such as COP (Crystal Originated Particle) are incorporated into a silicon single crystal produced by the CZ method, and if such crystal defects exist in a device fabrication region in the vicinity of a wafer surface, device characteristics such as an oxide film dielectric break down strength are degraded.
As a resort to remove such grown-in defects from a wafer surface layer, a method has been adopted in which a CZ silicon single crystal wafer W is subjected to high temperature heat treatment, for example, at 1200° C. for one hour in a hydrogen atmosphere or an argon gas atmosphere. By the high temperature heat treatment, grown-in defects in the vicinity of a surface of a CZ silicon single crystal wafer are annihilated so that there is obtained a silicon single crystal wafer having a high quality DZ (Denuded Zone) layer in the wafer surface layer (hereinafter referred to as an annealed wafer).